Fluorination of saturated halocar



to pass the halocarbon in vapor form through the vessel. The process isfrequently carried outfby distributing a shallow layer of leadtetrafluoridc throughout the length of a metal'tube and passing'asaturated halocarbon in vapor form through the tube. If desired, tubeswith rectangular cross section may be used and the exposed surface-ofthe layer of lead tetrafluoride thus increased. The mass may beagitated, if desired. The physical form of the-lead tetrafluoride ispreferably such that easy'penetration of the mass of tetrafluoride bygases 0r vapors passing through the reaction vessel is facilitated.Granulatedor coarsely powdered lead tetrafluoride has been found to besatisfactory. i

The reaction vessel, which may be of iron, nickel or other materialresistant to the reactants and. reaction products under the conditions,of fluorination andv regeneration, is maintained at-a desired reactiontemperature by-any convenient means. Heating may be effected in any oneof a number of ways, such as by electrical resistahce heaters, by gasflames, or by immersing thereaction vessel in a suitable high-boilingliquid, such as a low-melting alloy. The fiuorinationreaction isexothermic in nature and in large size reaction vessels heating may notbe necessary after the reaction has started. In some instances, coolingmay even be advisable. I

Fluorination 'of' a saturated halocarbon with lead tetrafiuoride may becarried out with the halocarbon reactant in either liquid or gaseousphase. In practice, however, it has usually been found more convenient,especially when high temperatures are required, to pass the halocarbonreactant through the reactor in vapor form. In this way, the handling oforganic liquids at high temperatures is avoided and the reaction may becarried out at ordinary pressures. A saturated halocarbon reactant maybe introduced into the reaction vessel either in the form of its vaporor as a liquid. In the latter instance, the halocarbon is usuallyvaporized in the portion of the reaction vessel nearest the entry portand the vapors are then fluorinated as they pass through the. remainingpart of the vessel. In certain iiistances, 'the halocarbon reactant maybe heated in a vessel separate from the fluorination vessel, a stream ofinert gas, such as nitrogen, hydrogen fluoride, or helium, passedthrough theheated liquid, and the mixed vapors of inert gas and ofsaturated halocarbon reactant then passed into the fluorination vessel.Fluorination with. the halocarbon reactant in the vapor phaseisconveniently carried out at atmospheric pressure although it may, ifdesired, be carried out at a pressure higher or lower than atmosphericpressure.

Although fluorination of a saturated halocarbon in the vapor phase usinglead tetrafiuoride as the active fluorinating agent is usually carriedout at a temperature between about 0 C., and about 500 C., it may becarried out at any convenient temperature above the condensingtemperature of the vapors at the reaction pressure. In certaininstances, the temperature of fluorination' may even be maintainedsufficiently high to cause fluorinolysis. Temperatures sufiiciently highto cause the formation of substantial amounts of undesirable byproductsare to be avoided.

' 'After'the lead tetrafiuoride has been largely exh'austed andconverted substantially to lead difluoride, thereaction vessel may bepurged with of the organic substances before elemental fluorine isadmitted to the reaction vesselto regenerate lead tetrafluoride. In thisway the possible explosive reaction of residual organic vapor withelemental fluorine within the reaction vessel is avoided. Regenerationof the spent lead tetrailuoride is, as noted above, carried out at atemperature above about C., preferably at a temperature between about250 C. and-about 500 C.

As mentioned previously the process of the invention may, if desired, becarried out with the saturated halocarbon reactant in the liquid phasein which case the halocarbon and lead tetra fluoride may be mixedtogether in any convenient way, e. g., the halocarbon may be stirred' ina vessel at the desired temperature and lead tetrafiuoride addedgradually thereto. Such procedure withthe halocarbon reactant in theliqiiid phaseis of particular value when the halocarbon boils at a hightemperature. It has been found thatthat ratio of the amount of leadtetrafluoride'to the amount of saturated halocarbon reactant necessarywhen a high degree of fluorination is to be effected is so great thatwhen the reaction is carried out with the halocarbon reactant in liquidphase the final reaction mixture is frequently of a moist granularnature rather than of a fluid nature and is difficult to handle on alarge scale. This difliculty may be overcome in a number of ways. Thusthe liquid which is to be iluorinated' may be diluted with a liquidinert under the reaction conditions, such as ahigh boiling fiuorocarbon, to increase the proportion of liquid in the reaction mixture.

Alternatively, fluorination in the liquid phase may be carried outstep-wise. Thus in the first step the addition of solid leadtetrafluoride to the liquid halocarbon reactant may be stopped while themixture is still fluid enough to be agitated readily. The reactionproduct may be filtered or otherwise treated to separate the organic andinorganic portions thereof, the spent lead tetrafiuoride regeneratedwith fluorine, and

the partially fiuorinated organic portion then fiuorinated further byadding to it, fresh or re- Although the in--:

generated lead tetrafluoride. vention is not limited to vapor phaseprocedures,

it is readily apparent that in many instances thev fluorination reactionis more conveniently carried out in vapor phase.

The degree of fluorination effected is dependent, amongother factors,upon the reaction temperature and the time of contact of the halocarbonreactant with lead tetrafluoride. In order to effect ahigh degree offluorination, e. g.,

perfiuorination, of a saturated halocarbon in the vapor phase during asingle pass through the reaction vessel, it may be necessary to pass thehalocarbon vapor very slowly through the vessel thus limiting the rateat which a highly fluorinated product may be produced in any particularreaction vessel. It has also been found that many halocarbons aresomewhat more thermally unstable in the unfiuorinated or only lowlyfluo-" rinated state than whenthe' are mor highly fluorinated and that,when it is attempted to fiuorinate such unfiuorinated or lowlyfluorinated halocarbons to produce a highly fluorinated halocarbonduring a single pass of the vapor through the fluorination vessel, itmay be necessary to elevate the temperature to such a degree thatundesirable decomposition of the halocarbon reactant is effected beforesubstam tial fluorination occurs.-

For these. and; other reasons. it is. som im s convenient.-. and;desirable. to recycle the halocar; bon reactant. after it i has been;partia ly uQrl:

has: been regenerated to insure ther being a high, proportion of leadtetrailuoride. in the leacl This recycl n of the. organic productemay berepeated afi; times as; is. desirable ornecessary. tointroduce thedesired;

fluoride mass.

p portion of; fluorine; into the;molecule and; each recycling ispreferably, but not-necessarily carried out at-a temperature-higher thanthe precede ne- K e and duringwhich relatively unstable halocarbons may.be;- present in, the; fiuorination'vessel are carried: outeatarelatively-v low temperature while a er; s a o fiiwr t mw ch usu lyequire a higher temperatureland during which:

tetrafluoride and; each maintained at a reaction,

temperature, which may, if desired, be higher thanthat of the precedingvessel. Bya suitable arrangement ofanumber of reaction vessels in seriesthe. process may be carriedout continuously it-; being. only necessaryto by-pass the, vaporsof-thehalocarbon reactant around any one o-l?the-reaction vessels while. thespent lead tetrafluori'de therein isbeing regenerated, with fiuorina tobe noted that a chlorine, bromine oriodine atom replaced with a fluorine-atom during the fluorinationappears in the reaction prodduct inelemental form; The efiiuent vaporsfrom the reaction thus contain, in addition to the desired saturatedfluorineecontaining. halocarbon. ahalogen other than fluorine, andmaycontain unfiuorinated or partially fiuorina'ted saturated halocarbonreactant. u

The reaction product is treated in any conven lent mannerto recovertherefrom the desired sat urated fluorine-containing halocarbon. One c1- venientw'ay in the case of vapor phase fluorination consists incooling and condens nathe efiiuent vapors and treating the condensedliquid to separate therefrom the desired saturated fluofine-containinghalocarbon. Theliquid reaction product may be treated in any one of anumber or ways. Thus the liquid may be fracticnally distilled and thedesired fraction collected, or it maybe treated directly with a diluteaqueous alkali to free it from elemental halogen and then fractionallydistilled. In any event the desired fluorine-containing fraction may becollected;- and any'less highly fluorinated fractions mayif desired,lee-recycled to the fluorination vessel to increase thev proportion offluorine in-thetrac tion.

In the case of fiuorination with the saturatedhalocarbon reactant inthe'liquicl state, the reaction mixture maybe filtered or otherwise.treated to separate the organic and 'inorganic.

mental fluorine and recycled lathe process.- The organic constituentsmay be washed-:withwater; and-with dilute aqueousalkali to. free' themfrom elemental halogen andgthe mixture In this way the first stages of;fluo inati e hich o t q a ieh t n res;

;, nation vessel and the fluorine, content.of the in-- sufficientlyfluorinated halocarbon increased by further-treatment with fresh orregenerated lead. tetrafluoride.v Other ways of recovering the desiredfluorine-containing halocarbon from thereaction inixtureiwill beapparent to those familiar with the art-and the presentinvention isanotlimited as tosuohmethods of recovery.

Certainadvantagesof the invention may be. seen from thefollowingexamples, which are. given by way of illustration. only and arenot to.be,- construed aslimiting.

Example-*1 Animn tube. fitted with means for heating; at any. desiredtemperature wasv packed. 1oosely'..witli several mols of leaddichloride. The tube. and? contentswere heated at about 300 C.andianhydroushydrogen fluoride passed through the. tube for severalhours. Elemental fluorine was then passed. through the tube for severalhours fiuorinating saturated halocarbons. containing at. least one atom'of halogen other than fluorine.

Example 2 A' reactor containing lead tetrafiuoride simi-' lar to thatdescribed in Example 1 was: heated at C. and L5 mols of carbonvtetrachloride: was passed slowly through the reactor in vaporform over aperiod of eight'hours. Efiluentgases from the reactor were passedthrough a condenser cooled to asufiiciently low temperature tocondenseorganic constituents in the vapors.

The condensate was washed free of chlorine with.

alkali andthe washed mixture fractionally distilled. Fractionswereisolated consistingsub stantially of. monochlorotrifluoromethane, di;chlorodifluoromethane, and trichlorom'onofluorc- Ineth'ane,respectively.

Example 3 The fraction consisting essentially oftrichl'oro-'monofiuoromethane obtainedin Example 2"wasrecycled through afluorination reactor containing lead tetr'afiuori'de of a temperature of1509 to C. Effluent vapors were-condensed as in Example 2 The-condensatecontained substantial fractions ofdichlorodifiuoromethan'e andmonochlorotrifluoromethane.

Example 4.

The fractions consisting essentially of dichloro difiuoromethaneobtained in Examples 2 and--23 were combined and passed in vapor formthrough; a fiuorinationzreactor containing lead tetrafi'uo-i ride heatedat .150 to 170 C. The reaction-prod-' uct, obtained by condensing theefiluent' vapors from the-reactor, contained a large proportion ofmonochlorotrifluoromethane.

Example 5 Trichlorononafluorocyclohexane is heatedin a streamof nitrogenand the mixed vapors of the chlorofluoro compound andnitrogen passedslowly-through a fluorination reactor containing: leadrtetrafiuorideata; temperature of from: 300

' .1 BONS WITH TETRAFLUORIDE Earl r. McBee, La Fayette, Ind., andRichard M. Robb, Wilmington DeL, assignors ,to Purdue,

Research Foundation,

'poration of Indiana NoDrawing This'invention relates to'organiccompounds containing fluorine, particularly to saturatedfluorine-containing halocarbons, and to a method for the .preparationthereof. This application is a continuation in partof applicationsSerial No.' 552,016,} filed August 3.0, 1944, now U. S. l ='atent No.2,533,132,issued' December 5, 1950, Serial No; 568,939,'fi1ed December19, 1944, and. Serial No. 572,257, filed January 10, 1945, nowabandoned.

The preparation of fluorine-containing haloca'rbons, i. e., offluorine-containin compounds composed entirely of carbon and halogen,has,'in most instances, heretofore been attended. with considerablediflic'ulty'. It is well known that elemental fluorine generally ,maynot be reacted with organic compounds, even with halohydro carbonscontaining alow proportion of hydrogen; and the reaction controlled soas to produce a desired fluorine-containing halocarbon' Al-, thoughcertain halogens other than fluorine, e. g.; chlorine and bromine, .may.react with a wide variety of organic compounds under suitable con--ditions to give high yields of valuable products;

the reaction of fluorine with most organic compounds is violent in'natureand is usually'accompa ned by profound d'ecompositi'on of the oranic" compound. In most "cases; reaction occurs with eiiplosiveviolencein spite o'f'extrefne measures which may be taken to moderateits effect. In many instances, the reaction products consist mainly ofcarbonaceous matter and hydrogen fluoride or of "other equallyundesirable products. When using a largeexcess offluorine the prin-'cipal products are generally carbon tetrafiuoride and hydrogen fluoride,Many -attempts have-;been made to use fluorinatin' agents other thanelemental fluorine to replace halogen or hydrogen in organic compoundsto obtain desired fluorine-containing or ganic compounds, e.g.,,fluorine-containing halocarbons. Among the fluorinating' agentswhich have been tried may be mentioned hydrogen fluoride, antimonytrifluorid'e, mercuric fluoride, iodine pentafluori'de, brominetrifluoride, chlorine triflu'o'rida. and' many others. Although certainof these agents may, under certain conditions replacewith fluorine acertain proportion of an existing halogenatom other than fluorinealready in a h'alocarbon molecule, many of these agents are ingeneralexpensive to prepare and inconvenient to work with. Furthermore,highly fluorinated compounds, e. g., perfluorlnated compounds, are notusually obtained readily from the corresponding highly chlorinated,bromlnated La Fayette, Ind. a'cor- Application December 20, 1945, vSerial No. 6Z36,'26$ I a 2 2 or iodinated compounds using such agents.Ger-4 tain of the agents referred to, e. g., bromine tri-f fluoride,react with many organic compounds with explosive violence. 1

-. exchange of'halogen, to produce polymerized or unsaturated break-downproducts and frequent-f 1y do not lead to complete or uniformreplacement of chlorine, bromine or iodine with fluorine.- For these andother reasons fluorine-containing halocarbons have not heretofore beenavailable except in a-few instances, and industry has been deprived ofmany members of this valuable group of compounds. .T'he need for new andimproved procedures for the preparation of fluorine-com: taininghalocarbons is evident.

"It is, therefore, an object of the present inventionv to provide .amethod for the preparation of fluorine-containing halocarbons. Still afurther object is to provide a method whereby saturatedfluorine-containing halocarbons, including fluorocarbons, may beprepared from completely chlorinated, brominated or iodinated saturatedhydrocarbons. An additional object is to provide a method wherebyfluorine-containing halocarbonsmay be prepared from completelyhalogenated hydrocarbons containin two or more dif: ferent halogens. Anadditional object is to pro-. vide a method for increasing the fluorinecon-;.- tent of a halocarbon containing fluorine and another halogen.Anadditional object is to provide a method for preparing afluorine-contain: ing halocarbon whereby the formation of un desirabledecomposition or polymerization products is substantially avoided. Anadditional ob-' ject is to providea method for fluorinating a.

v isnot subject to certain of the disadvantages set forth above.

Still a further object is to provide a novel fluorinating agent capableof replacing. established halogen other than fluorine in satufrate'dhalocarbons with fluorine. Still an additional object is to providecertain new and novel fluorine-containing halocarbons, including fluo-,rocarbons and other highly fiuorinated products; Other objects willbecome apparent from the fol lowin specification'and claims.

Accordin to the present invention the. fore-,'

going and related objects are accomplished read ture a halocarboncontaining at least a higher;

proportion of fluorine than the halocarbon fluorinated. Leadtetrafluoridehas been found to be an excellent fluorinating agent forreplacing with fluorine halogen other thanfluorine in saturatedhalocarbons and, when the'fl'uori-nation reaction is carried out underconditions hereinafter d.e-

scribed, the reaction can be controlld without difficulty.

Substantially any desired proportion ofthe. maximum theoretical amountof fluorine can beintroduced into the halocarbon with the,.forn7ra.-;tion of little or no decomposition or polymerization products. Saturatedaliphatic and .alicyclic aloc l n u edin he a o j and polycarbocyclicnon-fused-ringhalocarbons, can be converted readily tofluorine-containin'g. halocarbons. Chlorine. bromine and iodine presentin the halocarbon reactantcah be replaced partially or completely withfluorine,- as desired. Examples of saturated;fluorine-containinghalocarbons containing at least. one halogen atom other than fluorinewhich-may beprepared by themethod of the invention include'monochlorotrifluoromethane, dichlo rodifluoroinethane,trichloromonofluoromethane, tetrachloro difluoro ethane,dichlorotetrafluoroethane, monobromoe monochlorotetrafluoroethane,monobromopentaq fluoroethane, dichlorodecafluorocyclohexane,.dichlorotetradecafluoroheptane; pentafluoromonoiodoethane,undecachloroundecafluorobicyclohex-y yl,dichlorohexadecafluoronaphthalene; and many others. Saturatedfluorine-containing halocarbons containing. at least onehalogen atomother than fluorinev in the molecule,- such asathose just mentioned maybe fluorinated :to form saturated halo'carbons: or? increased fluorinecontent; including fluorocarbons if desired.

' According to one modification of the present invention,saturated-fluorocarbons, i. e., saturated compounds containing onlycarbon and fluorine, may be obtained by contacting a saturatedhalocarbon containing at least one atom of halogen'other than fluorinein the 'molecule'wi'th lead tetrafluoride as anactive fluorinating'agent under such conditions and-for such time that all of such halogenatoms other than fluorine in the molecule is replaced by fluorine.Examples of fluorocarbons which" may be prepared by such perfluorinationprocedure include carbon'tetrafluoride, hexafluoroethane,dodecafluoropentane, dodecafluorocyclohexane, tetradecafluorornethylcyclohexane, perfluorobicyclohexyl; 'perfluoronaphthalene,and many others.

In certain instances, ruptureof the molecule may be effected with theformation of saturated fluorine-containing halocarbons. having. fewer;carbon atoms in the molecule thandoes the orig inal halocarbonfluorinated/ This is herein re; ferred to as fluorinolysis. Thus, forexample, high molecular weight saturated halocarbons may be convertedlargely to high,. molecular weight fluorine containing halocarbons,torhigh molecular weight saturated fluorocarbjons or, under morevigorous reaction conditions to satu.- rated fluorine-containinghalocarbons or fluorocarbons having fewer carbon. atoms in' themole:

cule, such as hexafluoroethane and even carbon tetrafluoride, ifdesired.

Although the fiuorination reaction is exothermic, it proceeds withoutexplosive violence and may be controlled readily so as to produce ahalocarb'on containing substantially any des'ired' proportion offluorine. The fiuorination reaction is carried out at a temperaturebetween about 0 C., or somewhat lower, and about 500 .--C., or somewhathigher, preferably between about 2.0 OJ; and about 450 0.

During the,c.ourse. of the reaction, the lead tetrafluoride used as afluorinating agent, is converted to lead difluoride from which leadtetra-fiuoride'rmay be regenerated readily by exposing the difiuoride toelemental fluorine at an elevatedtemperature. The reaction may thus becarried out in cyclical manner, the lead tetrafluoride-being firstcontacted with a saturated halocarbon reactant to :produce a desiredsaturated fluorine-containing. halocarbon and the spent leadtetrafluoride consi'sting largely of lead difluoride, then regeneratedwithelemental fluorinev and. the cycle repeated. Furthermore, it may .bedesirable in some instances when a highly fluorinated saturated'halocarbon. is desired, td

efiectonly partial fiuorination in the first pass. sageof the.halocarbon ,reactantthrough the fiuorination reactor and. then torecycle the fluorine-containing product over regenerated or fresh leadtetrafluoride to increase the proportion of fluorine, in the halocarbonmolecule; Recycling: of the fluorine-containinghalocarbon as welras ofthe lead fluoride maybe continued 1111-.

. tilfthe fluorocarbonis;..obtained,.,if desired.

Lead tetrafluorid'e' isa solid which. is unstable in the presence ofwater or atmosphericmoisture. The compound is substantially stable,

when dry} at temperaturesas high as 500 C1 and higher. Leadtetrafluoride may be; prepared readily in a number of ways, oneconvenient way being bythe treatment of anhydrous lead di fluoride. withelementalfluorine. at an elevated temperature,v e. g., at a temperatureabove; about C, preferably at a temperature-between about 250?5-andabout 500 C. Lead'clifluoride may be preparedreadily by treatinganhydrous lead dichloride with hydrogen fluoride at temperatures aboveabout 159'? CE, and in manyother ways,

In practicing the invention; it has been found convenient to placeanhydrous lead dichloride in the reaction vessel; in which, thesubsequent fiuorination o'f a .halocarbon istobe carried out, and thentotreat the lead dichloride in the yessel, first with'hydrogen fluorideand then with elemental fluorine, under the said requisite condition oftemperature. Followin the fiuorination of ,a saturated halocarbon thespent lead tetrafiuoridek h h. ertain? a ar e: IQPQ fiQ of ,leaddifluoride, may .be regenerated and the difluoride reconverted to thetetrafluoride; by passing elemental fluorine over it at an elevatedtemperature. Thus, theconsumption or lead salts inthe process reducedtoaminimumand consists only of such negligiblequantitiesas may, be. lostmechanically during the process.

Fluorination of a. saturated-halocarbon with lead ,tetrafluoride maybecarriedoutinuany con: venient manner and' -in. any convenient type.of, apparatus. lt hasbeen foundsatisfactor todis pose the leadtetrafluoridein;athln layer, e. g,,, in a layer .from. about one-haltto. about. one inch thichonshelves or trayswithln the reaction ves. selor directly onthefltior of :the vessel itselfcand to 350 C. The productobtained by cooling the efiluent vapors from the reactor and treatingthe condensate with alkali to remove free halogen and acidic substancesconsists of substantial proportions of dichiorodecafluorocyclohexane,monochloroundecafluorocyclohexane, and perfluorocyclohexane.

The fractions obtained which contained one and two chlorine atoms in themolecule were each recycled through a fluorination reactor containinglead tetrafluoride at 300 to 350 C. and the eiiluent vapors treated asdescribed above. In each instance the reaction product contained a highproportion perfluorocyclohexane,

Example 6 Hexachloroethane is heated in a vessel to a temperature ofabout 180 C. and a stream of nitrogen passed through the vessel. Themixture of nitrogen and of vapors of hexachloroethane are conductedthrough a reactor filled with finely granulated lead tetrafluorideheated at a ten1perature of 309 to 350 C. The effiuent vapors arecollected in a cooled receiver, the condensate Washed with water anddilute alkali and fractionally distilled. Substantial fractions ofdichlorotetrafluoroethane and trichlorotrifluoroethane are thusobtained.

Upon recycling the two fractions just mentioned through a heatedfluorination reactor containing lead tetrafluoride and collecting andpurifying the reaction-product as before, perhaloethanes of increasedfluorine content, including perfluoroethane, are obtained.

Other saturated halocarbons containing at least one halogen atom otherthan fluorine which are reacted with lead tetrafluoride in a mannersimilar to those described in the foregoing examples to yield compoundsin which either all or a part of the halogen other than fluorine hasbeen replaced with fluorine include trichlorornonobromomethane,tetrabromodichloroethane, pentachloromonoiodoethane,pentachloropentafluorobutane, monobromomonochlorotetrafluoroethane,tetrachlorodecafiuoromethylcyclohexane,tetrachlorotetradecafluorodecahydronaphthalene, and many others.

We claim:

1. The process for the fluorination of a saturated polycarbon halocarbonto replace, with fluorine, all halogen atoms other than fluorine withretention of the carbon skeleton of the molecule, which includes thesteps of (1) vaporizing a saturated polycarbon halocarbon containing inthe molecule at least one halogen atom other than fluorine, (2) heatingthe vapor of the saturated halocarbon in contact with lead tetrafluoridein a reaction zone maintained at a temperature between about and 500degrees centigrade to cause replacement, with fluorine, of all halogenatoms other than fluorine in the molecule, and (3) condensing from theefiluent product a saturated compound containing only carbon andfluorine and having the same carbon skeleton as the starting saturatedpolycarbon halocarbon.

2. The process of claim 1, wherein the starting halocarbon is apolycarbon alkane halocarbon.

3; The process of claim 1, wherein the starting halocarbon is a2-carbon-atom halocarbon.

4. The process of claim 1, wherein the starting halocarbon is achlorofiuorocyclohexane.

EARL T. McBEE. RICHARD M. ROBB.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,004,932 Daudt et a1 June 18,1935 2,013,035 Daudt et a1. Sept. 13, 1935 2,024,008 Midgley et al. Dec.10, 1935 2,062,743 Daudt et a1 Dec. 1, 1936 2,192,143 Midgley et a1 Feb.27, 1940 2,220,713 Grosse et a1. Nov. 5, 1940 2,238,242 Balon et al Apr.15, 1941 2,423,045 Passino et al June 24, 1947 FOREIGN PATENTS NumberCountry 7 Date 214,293 Great Britain Apr. 14, 1924 3141/31 Australia .1Jan. 20, 1933 429,591 Great Britain May 28, 1935 786,123 France June 3,1935 OTHER REFERENCES Henne et al.: J. A. C. 5., vol. 63, pages 3478-3479 (1941).

Dimroth et al.: Ber. deutsch Chem. Ges., vol. 64,'pages 516-522 (1931).

Wartenberg: Zeitschr. anorg. allgem. chem, vol. 244, pages 337-347(1940).

Moissan: Comptes rendus, vol. 130, pages 622, 627 (1900).

Rufi and Giese: "Zeit. Anorg. Allgem. Chem., vol. 219, pages 143 to 148(1934).

1. THE PROCESS FOR THE FLUORINATION OF A SATURATED POLYCARBON HALOCARBONTO REPLACE, WITH FLUORINE, ALL HALOGEN ATOMS OTHER THAN FLUORINE WITHRETENTION OF THE CARBON SKELETON OF THE MOLECULE, WHICH INCLUDES THESTEPS OF (1) VAPORIZING A SATURATED POLYCARBON HALOCARBON CONTAINING INTHE MOLECULE AT LEAST ONE HALOGEN ATOM OTHER THAN FLUORINE, (2) HEATINGTHE VAPOR OF THE SATURATED HALOCABRON IN CONTACT WITH LEAD TETRAFLUORIDEIN A REACTION ZONE MAINTAINED AT A TEMPERAUTURE BETWEEN ABOUT 150 AND500 DEGREES CENTIGRADE TO CAUSE REPLACEMENT, WITH FLUORINE, OF ALLHALOGEN ATOMS OTHER THAN FLUORINE IN THE MOLECULE, AND (3) CONDENSINGFROM THE EFFLUENT PRODUCT A SATURATED COMPOUND CONTAINING ONLY CARBONAND FLUORINE AND HAVING THE SAME CARBON SKELETON AS THE STARTINGSATURATED POLYCARBON HALOCARBON.